Posts moved here from the altitude capture thread
WIth the DFC90 if you press A/P in any attitude it will hold that pitch and roll.
What is the minimum roll angle for that to work?
In the autopilot world it is usually around 7 degrees of roll. Below that, it will level the wings.
AFAIK it will hold any roll or pitch to +/-10 degrees and 22 degrees of bank. The A/P can be engagedn within +/- 60 degrees of bank and +/- 30 degrees pitvh (demonstrated values, not absolute).
If you want “straight & level” you’d only press the Straight & Level button. This has the same engagement limits by POH but it was demonstarted that the DFC90 recovered the SR22 to straight and level from inverted flight and other extreme attitudes.
Flyer59 wrote:
it was demonstarted that the DFC90 recovered the SR22 to straight and level from inverted flight and other extreme attitudes.
I’d love to see that… [read: I don’t really believe it]. The same claim was made about the LVL button of the G1000/GFC700 Perspective, and it couldn’t even handle a spiral dive recovery. It made the right inputs, but was far too slow in pitch so I had to help it avoid going above Vne.
The LVL button is a great idea, but it more suitable for the “what does it do now?” situations (instead of the usual A/P disconnect, which increases workload). The new “ASP” functions (which prevent severe pitch and bank excursions with the autopilot off) are more important to prevent loss of control, and of course once you ARE out of control, there always is the parachute.
Or, in other words, I would train a pilot who ends up inverted without intending to do so to pull the chute, not press a button and hope for the autopilot to put it right.
Just watch the video that shows the recovery from a roll, it’s on youtube. Or i can find it when i’m home.
I have done it from 80 degrees bank a couple of times, worked perfectly.
Here it is: that was even a test by AOPA
You bet i did. But they also said it recovered from all the mentioned maneuvers, rolls, loops, inverted, immelman. Very impressive i think, and i don’t think AOPA has much reason to make that up.
Nobody expected it to recover from a spin.
That was the article in AOPA magazine:
Avidyne’s new autopilots are equipped with a “straight & level” button designed to prevent pilots from becoming disoriented or losing control of their aircraft.
A pilot hand-flying an airplane with a DFC90 or DFC100 autopilot can simply push the S&L button, and that engages the autopilot and commands it to right the aircraft. But does the S&L feature work in all loss-of-control scenarios?
The FAA certifies autopilots to operate within 30 degrees of pitch and 60 degrees of roll. But a steep spiral or an encounter with severe turbulence or wing-tip vortices could exceed those limits. Would the S&L feature on Avidyne’s new attitude-based autopilots work in those scenarios? In an effort to better understand this new technology, AOPA Pilot Senior Editor Dave Hirschman took an Experimental-category Cirrus SR22-G3 into some extreme attitudes and used the S&L button on a DFC90 autopilot to recover. Here’s what he found:
“It goes against all of a pilot’s instincts and training to put the airplane in an unusual attitude and then let the autopilot take over,” said Hirschman, a veteran aerobatic pilot and Cirrus instructor. “But that’s exactly what we did here—and the results were both consistent and remarkable.”
Hirschman performed a series of aileron rolls to the left and right. Using a high-cruise power setting and an entry speed of 160 KIAS, he’d pitch the nose up 35 degrees, roll the airplane inverted, and engage the autopilot through a single push of the S&L button. Each time the autopilot guided the airplane back to level flight.
“The recoveries were smooth and authoritative and didn’t place extraordinary stress on the airframe,” Hirschman said.
According to the airplane’s flight data recorder, the autopilot took about two seconds to take over once the S&L button was pushed. Then it commanded rolls up to 25-degrees-per-second until the wings were level. The nose of the aircraft fell about 40 degrees during the recoveries, and indicated airspeed increased from 100 knots when the autopilot was engaged to a maximum 185 knots (VNE is 201 KIAS) during the pull-out. Acceleration during the recoveries ranged from negative 0.5 Gs to a positive 2.5 Gs, well within the aircraft’s normal operating envelope of negative 1.56 Gs to positive 3.89 Gs. Beginning at an altitude of 10,000 feet, the aircraft lost about 1,800 feet during each recovery. Hirschman manually reduced the throttle to avoid gaining excessive speed.
“The S&L button isn’t a ‘Get out of jail free card’ and it won’t solve every conceivable problem from in-flight loss of control,” Hirschman said. “An aerodynamically clean aircraft like the SR22 can develop excessive airspeed during the recovery, and altitude loss can be significant. Also, the autopilot isn’t linked to the rudder, so it won’t command a spin recovery because it can’t apply opposite rudder.
“But the S&L feature works far beyond the pitch and roll limits for which autopilots are certified, and I wouldn’t hesitate to use it in an emergency—or to prevent an emergency situation from developing in the first place.”
35 degrees nose up, 100kt, and inverted —> nose dropped to -5 degrees and speed peaked 16kt below Vne, lost 1,800ft.
Exercise for the reader: assume a start with nose at the horizon, inverted, at cruise speed. What do you think the lowest attitude, peak speed, and altitude loss will be?
Also, most people do not lose control in a botched roll.They enter a spiral dive (most of the time), or a stall in the climb to the top (rarely). Typically, they notice the spiral dive when the air noise increases significantly. At that point, they are likely to have 45-60 degree+ angle of bank, the nose well below the horizon, descent rate pegged at the bottom stop and the airspeed rapidly heading towards Vne.
As I said above – GFC700, not DFC90, though – the autopilot was acting correctly, but was too slow to make the corrections and not bust Vne, and that was with me pulling the throttle to idle. Now a Vne exceedance is not instant death, but still.
Doesn’t mean the autopilot is poor, but it makes the AOPA pilot’s statement
I wouldn’t hesitate to use it in an emergency
If you lose control to the point you already are in a steep spiral dive, the appropriate system to use it the parachute. Only if there is sufficient altitude to attempt a recovery you should attempt a recovery, LVL button or manual. Figuring out if you have altitude to attempt a recovery will take precious time you might not have.
Only if there is sufficient altitude to attempt a recovery you should attempt a recovery, LVL button or manual.
Every Cirrus pilot knows that CAPS is the only way if there’s not enough time/altitude.
I still find the technology impressive, and it will recover the airplane from many abnormal attitudes, which might be helpful every now and then, for example if you were in IMC and about to lose control, for example due to vertigo. You could gain some time by pressing the LVL button …
As always, you have to know the limits.
